Tens of thousands of Iranians defied a ban to protest against last week’s hotly disputed presidential election result as the authorities struggled to contain anger among the reformist opposition.

Chanting crowds, some wearing green campaign colours, greeted Mir Hossein Mousavi, the defeated candidate in Friday's poll, as he moved slowly through the streets on the back of a four-wheel drive car.

Scufflles broke out as supporters of Mr Ahmadinejad, riding motorbikes and armed with sticks, attacked the demonstrators along the route.

"The vote of the people is more important than Mousavi or any other person!" said Mr Mousavi, standing on the car roof in Revolution Square and speaking through a loudhailer.

The crowds of young and old who packed several miles of his route, shouted back: "Mousavi we support you! We will die but retrieve our votes!"

They took up protest chants: "Where are the 63 per cent who voted for Ahmadinejad? If Ahmadinejad remains president we will protest every day."

Both Mr Mousavi and Mehdi Karroubi, another defeated candidate who appeared alongside him today, have lodged complaints that the vote was rigged.

Some of the results – which awarded a record-breaking 25 million votes to President Ahmadinejad – were announced before the ballot boxes had even been opened.

Today it emerged that Ayatollah Ali Khamenei, Iran's Supreme Leader, has been forced by the strength of public opinion to perform a U-turn and back an election inquiry.

On Saturday Ayatollah Khamenei declared that the victory by Mr Ahmadinejad, his political creature, was not merely fair but a "divine intervention".

"This is a turnaround for Khamenei, and it's an embarrassing one," said Professor Ali Ansari, the director of the Iranian Institute at St Andrews University.

Today was the first time that Mr Mousavi had been seen in public since the election, as the authorities clamped down hard on protests, vowing to crush any "velvet revolution" in Iran.

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